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A Mother Cell-Specific Class B Penicillin-Binding Protein, PBP4b, in Bacillus subtilis. Yuping Wei, 2004.The Bacillus subtilis genome encodes 16 penicillin-binding proteins (PBPs), some of which are involved in synthesis of the spore peptidoglycan . The pbpI (yrrR) gene encodes a class B PBP, PBP4b, and is transcribed in the mother cell by RNA polymerase containing  E .
Loss of PBP4b, alone and in combination with other sporulation-specific
PBPs, had no effect on spore peptidoglycan structure .
YfcX Enables Medium-Chain-Length Poly(3-Hydroxyalkanoate) Formation from Fatty Acids in Recombinant Escherichia coli fadB Strains. Kristi D. Snell, 2002.Expression of Escherichia coli open reading frame yfcX is shown to be required for medium-chain-length polyhydroxyalkanoate (PHAMCL) formation from fatty acids in an E . coli fadB mutant . The open reading frame encodes a protein, YfcX, with significant similarity to the large subunit of multifunctional ß-oxidation enzymes . E . coli fadB strains modified to contain an inactivated copy of yfcX and to express a medium-chain-length synthase are unable to form PHAMCLs when grown in the presence of fatty acids . Plasmid-based expression of yfcX in the FadB- YfcX- PhaC+ strain restores polymer formation . YfcX is shown to be a multifunctional enzyme that minimally encodes hydratase and dehydrogenase activities . The gene encoding YfcX is located downstream from yfcY, a gene encoding thiolase activity . Results of insertional inactivation studies and enzyme activity analyses suggest a role for yfcX in PHA monomer unit formation in recombinant E . coli fadB mutant strains . Further studies are required to determine the natural role of YfcX in the metabolism of E . coli . Identification of the Clostridium perfringens Genes Involved in the Adaptive Response to Oxidative Stress. V. Briolat, 2002.Clostridium perfringens is a ubiquitous gram-positive pathogen that is present in the air, soil, animals, and humans . Although C . perfringens is strictly anaerobic, vegetative and stationary cells can survive in a growth-arrested stage in the presence of oxygen and/or low concentrations of superoxide and hydroxyl radicals . Indeed, it possesses an adaptive response to oxidative stress, which can be activated in both aerobic and anaerobic conditions . To identify the genes involved in this oxidative stress response, C . perfringens strain 13 mutants were generated by Tn916 insertional mutagenesis and screened for resistance or sensitivity to various oxidative stresses . Three of the 12 sensitive mutants examined harbored an independently inserted single copy of the transposon in the same operon as two genes orthologous to the ydaD and ycdF genes of Bacillus subtilis, which encode a putative NADPH dehydrogenase . Complementation experiments and knockout experiments demonstrated that these genes are both required for efficient resistance to oxidative stress in C . perfringens and are probably responsible for the production of NADPH, which is required for maintenance of the intracellular redox balance in growth-arrested cells . Other Tn916 disrupted genes were also shown to play important roles in the oxidative stress response . This is the first time that some of these genes (e.g., a gene encoding an ATP-dependent RNA helicase, the ß-glucuronidase gene, and the gene encoding the atypical iron sulfur prismane protein) have been shown to be involved in the oxidative response . Analysis of the Mobilization Region of the Broad-Host-Range IncQ-Like Plasmid pTC-F14 and Its Ability To Interact with a Related Plasmid, pTF-FC2. Leonardo J. van Zyl, 2003.Plasmid pTC-F14 is a 14.2-kb plasmid isolated from Acidithiobacillus caldus that has a replicon that is closely related to the promiscuous, broad-host-range IncQ family of plasmids . The region containing the mobilization genes was sequenced and encoded five Mob proteins that were related to those of the DNA processing (Dtr or Tra1) region of IncP plasmids rather than to the three-Mob-protein system of the IncQ group 1 plasmids (e.g., plasmid RSF1010 or R1162) . Plasmid pTC-F14 is the second example of an IncQ family plasmid that has five mob genes, the other being pTF-FC2 . The minimal region that was essential for mobilization included the mobA, mobB, and mobC genes, as well as the oriT gene . The mobD and mobE genes were nonessential, but together, they enhanced the mobilization frequency by approximately 300-fold . Mobilization of pTC-F14 between Escherichia coli strains by a chromosomally integrated RP4 plasmid was more than 3,500-fold less efficient than the mobilization of pTF-FC2 . When both plasmids were coresident in the same E . coli host, pTC-F14 was mobilized at almost the same frequency as pTF-FC2 . This enhanced pTC-F14 mobilization frequency was due to the presence of a combination of the pTF-FC2 mobD and mobE gene products, the functions of which are still unknown . Mob protein interaction at the oriT regions was unidirectionally plasmid specific in that a plasmid with the oriT region of pTC-F14 could be mobilized by pTF-FC2 but not vice versa . No evidence for any negative effect on the transfer of one plasmid by the related, potentially competitive plasmid was obtained . Conservation of Ornamental Stone by Myxococcus xanthus-Induced Carbonate Biomineralization. Carlos Rodriguez-Navarro, 2003.Increasing environmental pollution in urban areas has been endangering the survival of carbonate stones in monuments and statuary for many decades . Numerous conservation treatments have been applied for the protection and consolidation of these works of art . Most of them, however, either release dangerous gases during curing or show very little efficacy . Bacterially induced carbonate mineralization has been proposed as a novel and environmentally friendly strategy for the conservation of deteriorated ornamental stone . However, the method appeared to display insufficient consolidation and plugging of pores . Here we report that Myxococcus xanthus-induced calcium carbonate precipitation efficiently protects and consolidates porous ornamental limestone . The newly formed carbonate cements calcite grains by depositing on the walls of the pores without plugging them . Sonication tests demonstrate that these new carbonate crystals are strongly attached to the substratum, mostly due to epitaxial growth on preexisting calcite grains . The new crystals are more stress resistant than the calcite grains of the original stone because they are organic-inorganic composites . Variations in the phosphate concentrations of the culture medium lead to changes in local pH and bacterial productivity . These affect the structure of the new cement and the type of precipitated CaCO3 polymorph (vaterite or calcite) . The manipulation of culture medium composition creates new ways of controlling bacterial biomineralization that in the future could be applied to the conservation of ornamental stone .
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